This invention relates generally to ball studs used in ball joints, and in particular to an anti-rotation ball stud head particularly useful for connecting a headlamp adjuster to a socket on the reflector of a headlamp assembly.
Ball joints typically include a ball stud pivotally engaged in a socket. Such joints have a wide variety of applications where a pivotable connection between two parts is desirable. For example, they may be used in many types of linear actuators and have been found to be particularly useful in automotive lamp assemblies. Automotive lamp assemblies used as headlights typically comprise several basic parts: a support frame, a reflector, a lens, a bulb, and one or more adjusters. The support frame either completely houses the reflector and the bulb on a pivotable mounting to allow the aim of the light to be adjusted using the adjusters or provides a mounting surface for attaching a headlamp adjuster. The lens seals the front of either the support frame or directly to the reflector to protect it from the elements assailing the front end of the vehicle and provides an aerodynamic shape and attractive appearance. The reflector mounts on one fixed ball joint and is adjustable horizontally and vertically using adjusters that interface with the reflector through moving ball joints. The moving ball joints are moveable by actuating the adjusters connected to the moving ball joints by a ball stud having a head and a shaft. A socket is used to secure the pivotable engagement of the ball stud to the reflector. Ball joints are required because of the many possible adjustments that may be made to the orientation of the reflector. If ball joints are not used, the reflector into which the adjusters are fitted will not be sufficiently adjustable because the reflector will not be positionable in both the vertical and horizontal directions. Right angle adjusters are often used to allow the adjustment of the headlight from an adjusting position above the installed headlight. In other applications, motorized adjusters, straight adjusters, or other types of adjuster are used.
In many headlamp adjusters, the ball stud moves when a threaded nut rotates around a threaded shaft section of the ball stud. Because rotation of the ball stud is restrained when the threaded nut rotates around the threaded shaft section of the ball stud, the ball stud moves along its axis with respect to the adjuster thereby effectuating adjustment of the headlamp. In many headlamp adjusters, the ball stud will undesirably rotate unless it is prevented from doing so by structure on the head of the ball stud, e.g., engaging tabs ("ears"). Examples of such adjusters are disclosed in U.S. Pat. Nos. 4,689,725; 5,161,877; and 5,186,531. Sockets used in connection with such adjusters must coact with the ball stud to prevent rotation thereof in order for the adjuster to function because if the ball stud is allowed to rotate, then it will not move along its axis to effectuate adjustment. One drawback to the use of such ball stud and socket combinations is that the ears on the ball stud head must be aligned with receiving slots in the corresponding socket when the stud is installed in the socket. This complicates automated assembly.
In other headlamp adjusters, rotation of the ball stud is restrained by mechanism provided within the adjuster itself, e.g., the "anti-rotation insert" disclosed in U.S. Pat. No. 5,707,133. Examples of other such adjusters are disclosed in U.S. Pat. Nos. 4,796,494; 5,034,870; 5,079,676; 5,163,746; and 5,775,795.
In the various types of adjusters described above, a socket is used to make the pivotable connection between the ball stud and the reflector. Examples of ball stud and corresponding socket combinations are shown in FIGS. 4 and 5 of U.S. Pat. No. 4,689,725; FIG. 2 of U.S. Pat. No. 5,161,877; FIG. 1 of U.S. Pat. No. 5,673,992; FIG. 2 of U.S. Pat. No. 5,095,411; and FIGS. 10-14 of U.S. Pat. No. 5,186,532. Additionally, at least the following U.S. patents are specifically directed toward ball joints for use in connection with headlamp adjusting mechanisms: U.S. Pat. Nos. 4,974,123; 5,047,904; and 5,063,481.
A "quarter turn" style ball socket that has been used in connection with headlamp adjusters (identified generally as 15) is shown in FIG. 1 and is identified generally as 20. As shown in FIGS. 3A and 3B, the quarter turn socket 20 is used in connection with a reflector 22 having a boss 24 extending therefrom. The boss 24 has a hole into which the quarter turn socket 20 is inserted and typically also has ramp locks 26. The quarter turn socket 20 has lugs 28 that protrude from the socket 20 which pass through the hole in the boss 24 when the socket 20 is inserted in the direction indicated by arrow 29 in FIG. 3A. The socket 20 is usually already joined with a conventional ball stud 30 (FIG. 3) prior to being inserted into the boss 24. After insertion, the socket 20 must be rotated a quarter turn to rotate the lugs 28 so that they will not be able to pass through the hole in the boss 24. This rotation also locks the socket 20 into the boss 24. In rotating the socket 20, flexible wings 32 extending from the socket 20 flex and slide over the ramp locks 26 on the boss 24. The wings 32 then snap down to prevent disengagement of the socket 20 from the boss 24 by further rotation of the socket 20 caused by rotational force imparted by the adjuster 15. Of course, ramp locks 26 may not be necessary if an adjuster 15 with internal anti-rotation, e.g. the one disclosed in U.S. Pat. No. 5,707,133, is used because no rotational force is imparted by the ball stud on the socket 20. When used in connection with a conventional ball stud 30 (FIG. 3), the quarter turn socket 20 cannot be installed to the boss 24 of the reflector 22 simply by rotating the ball stud 30. This is because the smooth finish on the conventional ball stud 30 allows the ball stud 30 to slip within the socket 20 upon rotation (indicated by arrow 33 in FIG. 3B) of the ball stud 30. Thus, a wrench or other tool that engages installation tabs 34 must be used to properly install the ball socket 20. The necessity of a special tool to complete the installation of the socket complicates installation and adds to the total assembly time of the headlamp assembly. Additionally, it is highly desirable to provide a quarter turn style socket for use in connection with a headlamp adjuster that also mounts using a quarter turn because the entire assembly can then be easily and efficiently installed in the headlamp assembly.
Additionally, existing quarter turn style ball sockets retain the ball stud in the socket using an undercut type interference. This interference requires an even wall thickness around the entire circumference of the socket in order to maximize retention of the ball stud (pull out resistance) and maintain a uniform stress distribution around the socket to prevent cracking during assembly of the socket over the ball stud head. Existing quarter turn sockets have no slots for receiving "eared" ball studs or other means to restrict ball stud rotation and therefore can only be used in connection with adjusters having internal anti-rotation capabilities.
Unsuccessful attempts have been made to provide ear receiving slots in quarter turn sockets for the purpose of allowing the sockets to be used in connection with adjusters that require an external rotation restraint, Additionally, unsuccessful attempts have been made to provide ear receiving slots in quarter turn sockets for use with adjusters having internal anti-rotation capabilities for the purpose of facilitating installation of a quarter turn adjuster/socket combination. When ear-receiving slots are added to the quarter turn style socket, the pull out resistance is reduced and the non-uniform wall thicknesses results in a concentration of stress at the slots.
Because of these problems, even if the use of ear-receiving slots in the socket were a viable possibility, there are manufacturing complications when attempting to form both ears on the ball portion of the ball stud and anti-rotation grooves or flats on the threaded shaft portion of the ball stud. Thus, even in adjusters having internal anti-rotation, such as the one disclosed in U.S. Pat. No. 5,707,133, the use of an eared ball stud to cause rotation of the quarter turn socket would be problematic.
In attempts to insert conventional eared ball studs into internally smooth quarter turn ball sockets (i.e., no ear receiving slots), it has been found that the ears press against the smooth inside walls of the socket and the resulting interference generates some resistance to rotation. However, this combination does not generate a very high level of anti-rotation resistance and, when the interference is increased (by increasing the size of the ears), the entire socket expands and does not fit into the hole in a standard size boss on the reflector. Additionally, each incremental increase in the size of the ears greatly increases the concentration of stress at the ear-socket interface which results in a higher risk of socket cracking. Thus, the use of conventional eared ball studs with quarter turn sockets is not effective.
Accordingly, a need exists for a ball stud head that can be easily installed in a quarter turn socket preferably without the use of tools, that can be used in connection with adjusters having internal anti-rotation mechanism and adjusters requiring anti-rotation at the ball stud head, that exhibits high anti-rotation characteristics and allows full pivotability, and that is cost-effective and easily manufactured and installed.